Bus or train from Germany to Wales?

S-Bahn operates a train from Berlin to Cardiff every 5 minutes. Tickets cost $1 and the journey takes 6 min. 5 other operators also service this route. Alternatively, BVG operates a bus from Berlin to Cardiff every 10 minutes. Tickets cost $3 - $5 and the journey takes 26 min. 3 other operators also service this route.